A joystick is a well-known mechanical actuator for a device that can be used to provide control input to electronic games and computers. Another, similar device is sometimes referred to as a directional control pad ("DCP"). A DCP device generally has an active area, usually circular, and is typically about one and a half inches in diameter. Application of pressure at various angular positions on the active area of a DCP produces a corresponding electrical output signal,
Most inexpensive controllers, of either the joystick or DCP type, provide only limited, coarse, output signals. This is due to the fact that these devices generate their output signals by the use of four momentary switches. Typically, four leaf switches or conductive rubber dome switches are used for end point detection in each of four possible directions of motion of the actuator of the controller, e.g., "North", "South", "East" and "West" directions. In general, these switches are spaced 90.degree. from each other around the periphery of the input device. In these devices, a given amount of motion solely in the "North" direction, for example, causes the closure of only the single switch used to detect motion in this direction. The same is true for motions exclusively in the "South", "East", and "West" directions. Motion of the joystick in a "North-East" direction,: can cause simultaneous closure of both the "North" and "East" switches. Likewise, dual switch closures will occur for joystick motion in the "North-West", "South-East", and "South-West" directions. Thus, there are only eight directions which can be represented by unique output states of such a simple device. Furthermore, in devices which use momentary switches, the output of the device merely indicates a switch being "on" or "off" and the output signal does not indicates a magnitude in that direction.
One significant problem with the electromechanical devices as described above is that they are subject to an increase in the resistance of the switch contacts due to, for example, wear, misalignment, oxidation, and accumulation of dirt. As the contact resistance increases, the switch begins to fail on an intermittent basis. Intermittent failures of an input controller are particularly unacceptable in a game environment where split second reactions by a user are often required. Devices based upon mechanical switches also suffer from the inherent variations from one switch to another, such as the gap between contacts and spring stiffness. These variations will result in inconsistent and uneven position indication from the control device, and provide inadequate sensitivity for certain applications of the device. Additionally, mechanical switches are also subject to switch bounce in which the output of the switch will oscillate between its "on" and "off" voltages for several milliseconds after being switched.
Some prior art input devices have used electro-optical mechanisms to detect the actions of the user. Mitchell, U.S. Pat. No. 5,117,102 describes relative motion detection device for a joystick which contains Light Emitting Diodes (LEDs) and optical detectors which are diametrically opposed about the shaft of the joystick. As the joystick is moved, the shaft itself blocks; the light from the LEDs and thus, the action of the user is, detected. Another typical prior art method of detection is disclosed in U.S. Pat. No. 4,748,323 to Holiday. In the joystick device taught in this patent, a circular disk is coaxially mounted on the lower portion of the shaft of the joystick. Four LED/detector pairs are mounted on C shaped blocks. Light from the LED to the detector passes parallel to the shaft's neutral position. As the shaft is tilted, the disk enters the open end of the C shaped blocks and occludes the light from the LED. Each of these prior art devices suffers from at least three problems. First, the simpler embodiments of these devices do not provide adequate resolution! of! the motion joystick and can only report. gross motions. Second, to attain a greater resolution, a greater number of component parts are required which increases the manufacturing cost of such a device. Finally, as more LED and detector combinations are added to these devices, the need to create light baffling between the light sources and light detectors is required.
It is therefore one object of the present invention to provide a practically infinite resolution of the angular direction of the motion or force applied to an input controller. It is an additional object of the present invention to indicate the amplitude of the motion or force applied in a specific direction. It is also an object of the present invention to decrease the cost of producing an analog control device. It is a further object of the invention to increase the resilience of an input device to conventional wear.